re: Silverado engine losing compression / dealership says it has to be replaced

Yes it does change your shift points and mine still went into v4 in tow haul. To really get rid of it you need to do some serious work. The tune does seem to help. I was starting to burn a little oil around 110k and I got a Diablo tuners that fixed it and now I have 180k. I also got to fix my tire size and play with my throttle sensitivity. I have a 2011